text:
Staying in pattern at a class C airport
Before departing VFR from a class C airport, I contact Clearance Delivery and tell them what I want to do. If I am just looking to stay in the pattern, though, what do I need to tell them?

Welcome to aviation.SE! Which country or regulations are you asking about?

I would tend to agree with Michael Hall that you probably don't need to contact Clearance Delivery if you are planning on remaining in the pattern. In general you should contact Clearance Delivery (if a frequency is published) if you want to be assigned a discrete squawk code. So:

At a Class D, you do not need to contact CD unless you are requesting an IFR clearance or VFR flight following.
At a Class C, you do not need to contact CD if you are requesting to remain in the pattern. All other departures, even if you do not want flight following, should contact CD to receive a "local" code out of the Charlie.
At a Class B, all departures should contact CD to receive a squawk code, even if you'll just be staying in the pattern. This is because ATC provides radar separation to all aircraft operating in Bravo airspace. (I don't know if you'll get many Bravo towers to approve pattern work though.)

If you just want to remain in the pattern, it would probably be acceptable to contact Ground directly and use the following phraseology:

Ground, N12345 is at the FBO, request taxi to runway 27 for pattern work, we have information Alpha.

But it might be worth a call to your tower to see how they want you to do it. Their procedure might be for the CD controller to prepare all departure strips and hand them to Ground, so they want you to call CD anyway. Or they may have no problem with you calling Ground first. Where I work, we're slow enough that Ground and Clearance are almost always combined anyway so it doesn't matter which one you call.

There would be no need to contact either clearance delivery or departure control if you intend to remain in the pattern.  This presumes that the control tower is operational, because they of course control the Class D airspace that holds the pattern.
I am not aware of any Class C airspace where the primary airport would not have a tower, or that the tower might close while Approach/Departure control remains active.  However, if this was the case, or if you were staying in the pattern at a secondary airport underneath or adjacent to the Class C, it certainly wouldn't hurt to give them a quick call and let them know what you are doing.


text:
I don't have a student pilot certificate number yet, can I still take the checkride?
Around May 25th, my instructor signed the IACRA for my student pilot certificate application, and I printed the (paper) temporary certificate. However, where it should list the a certificate number, it only says “PENDING”.
My hours are completed, and I am pretty much checkride ready.  But when filling out the online version of Form 8710, I am required to enter the number of my student pilot certificate.
We had a DPE lined up for this week, my all other requirements are completed. How do I complete the application without a certificate number?

You should probably ask the DPE you are scheduled with.  The temporary private pilot certificate they will issue when you pass will trump any student certificate, but you wouldn't want them to be surprised...

I think the answer is to put “PENDING” as the cert number, but I have no source. Your DPE has probably run into this before and should be able to confirm authoritatively.

The current processing date is June 4, fwiw.

My first question for you is how the hell did your current instructor solo you or allow you to accomplish your solo CC flights without a student pilot certificate?

Yes sir, I do have a student pilot certificate already, the issue is there has been no number assigned to it as of date (in the student pilot cert number it says "pending"), hence I was unsure how to proceed with the ppl application. The DPE instructed me to just put pending for now.

@CarloFelicione I’ve improved the clarity of what OP was asking.

According to MY DPE, the answer is to enter “PENDING" for my pilot certificate number in the IACRA application.

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sort: votes


text:
VFR through Class C to land at Class D (located within Class C)
Student pilot (US) here prepping for long solo XC. I'll be landing at a Class D airport (KSCH) within Class C airspace (KALB).
I have a few questions regarding procedure and what is appropriate for radio calls.  I assume my first call will be to approach control for the Class C airspace and state who I am, where I am, my altitude, have information, and my destination (the Class D airport).
My question is what exactly am I requesting?  Flight following?  Just request VFR to destination?  I assume at some point they will hand me off to the tower at the Class D airport.  In the meantime, am I able to change altitude through Class C as I begin a descent into Class D for landing or does it depend on what approach control advises?
Thanks for any help.

It would help us to know your destination airport as well, some airports have extra procedures.

Thanks.  Yes, I will certainly be discussing with my CFI.  But, I also like to prepare for those CFI discussions in advance by asking others as well.

KALB is the Class C.  Landing at KSCH.

Having just gone and looked at skyvector: SCH itself is solidly outside the ALB Class C surface area, but you can see how the Class D surface area intrudes slightly on the Class C surface area. For that small intrusion, the Class C overrides the Class D. The Class D ceiling is also infringed upon by the Class C 20-mile ring, and for that area too the Class C is overriding, so in that section the D really only goes up to [-20] instead of [29].

Thanks. Appreciate it.

First of all, there is no such thing as a Class D airport within Class C airspace. Airspace classes are exclusive; unless there is a cutout in the Class C (which there will be) the C will take precedence over the D.
Answering in the context of faa-regulations, what you should do is call the facility which owns the Class C airspace and say this:

You: Podunk Approach, Skyhawk 123AB, two-zero miles northwest of Podunk at three thousand five hundred, full stop at at Hicksville with information Alfa.
Approach: Skyhawk 123AB, Podunk Approach, radar contact, Podunk altimeter 29.92. Squawk 0101. Maintain VFR at or below three thousand five hundred.

In order to enter the Class C airspace you need to establish two-way communications with the controlling agency, which is Podunk Approach.
In order to enter the Class D airspace you need to establish two-way communications with the controlling agency, which is Hicksville Tower.
At some point Approach will tell you to contact Tower, and you should not switch frequencies before then.
Approach may assign you vectors or altitudes or both to ensure applicable separation between you and other traffic (which in Class C is either target resolution or 500' vertically from IFR traffic, and they will issue traffic advisories and safety alerts on other VFR traffic). It is still your responsibility to see-and-avoid and maintain applicable cloud clearance for the airspace you are in, and you must speak up if a controller's instruction will cause you to violate those clearances.
You do not need to listen to the ATIS for the Class C airport but you should listen to the ATIS for the Class D airport.

Thanks for the detailed response and apologies for the poor description.  I do recognize there is no Class D airport within a Class C airspace.  I would be passing through KALB airspace and landing at KSCH.   Thanks again.

@757: say there is an airport with C airspace with a surface area 5NM radius of the airport, and say there is an airport with D airspace only four miles away from the C airport. Even if the D airspace was defined as "3NM radius of the airport" the airport would still be within the C surface area because the C takes precedence. So in order for second airport to actually be within its own D surface area the C must be explicitly excluded from that area... which will obviously happen. In fact the C and D will probably be defined to not overlap, but if they did the C would override the D.

PDX Class C and Troutdale D overlap in altitude.  Just FYI if someone was looking for an example.

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text:
How do I calculate the impact of the winds aloft in this test question?
I was flying through this section in the ASA test prep book, I thought I had mastered this E6B.  But this has me stumped:

I can’t do the math to figure out how many knots I’ve traveled. But in the answer it has me plotting a course of 280 (100 + 180) from the departure point. I cannot figure out for the life of me where they got this course.
I see that the winds are from 100 in the winds aloft, but I can’t imagine how I get a 100+180 course from that.  I feel like I’ve missed some major concept.

If the wind is coming from 100 degrees, which direction will the plane be blown?

Ok, that helps.  280 is opposite 100.  Got it.  But isn’t it still making a lot of assumptions like no wind correction and such?

I'm not sure I understand the question. You didn't mention which heading or course the question asks you to fly from the airport. E.g. heading 100 would take you directly into the wind; 280 would take you directly away from it etc. Or are you just asking about the effect of the winds only, and not what they mean for the final track of the aircraft? If you could quote the entire question I think it would be a lot clearer.

@Pondlife That had me baffled too until I saw this is for the LSL (Light Sport-Lighter Than Air) test.

I didn't notice LSL, but with airspeed matching wind I was just starting to question whether this was for a balloon!  @rbsc, did you realize this?!

First of all, make sure you’re only doing the questions that will actually be on the test you’re taking. This specific question is only for the LSL question bank, so unless that’s what you need, forget it and move on.
In a balloon, you will be carried by the winds aloft. If the wind is from 100@8, then your track will be to 280@8.
First, use your protractor to draw a track line on a track of 280 from the point of departure. This shows your balloon’s track over the ground.
Next, multiply 8 by the (decimal) number of hours you will be in the air, and then use your scale to mark that distance along the track line. That’s how far your balloon will have traveled at the specified time.
No need for an E6B here.

Son of a..   No.  I sure did not realize this was a balloon question.   Makes so much more sense now.  Face palm.  Thanks to you all!


text:
Can I work in USA aviation maintenance without U.S. citizenship?
I am currently working outside of the US but have all the aviation maintenance degrees, and I am moving to the US.
Can I work in the USA if I don’t have citizenship?

Does this answer your question? How can I be US aircraft maintenance technician?

This question is about immigration & employment law, not aviation.

Suggest migrating to Expatriates.stackexchange

I’m not sure if there is an SE group for immigration and naturalization questions, but that would seem to be more related to that than aviation.

I’m voting to close this question because it is more likely to be answerable in [expatriates.se]


text:
Has a commercial or military jet bi-plane ever been manufactured?
Are there any, or have there ever been any commercial/military jet bi-planes?
What would be some of the major advantages vs disadvantages if one was built?

Electric radio controlled ducted fan model.

University of Tokyo concept model.

When searching this site for "jet biplane", the second hit is https://aviation.stackexchange.com/questions/33679/ - The answer is the same as the currently highest voted answer to your question. - I'm calling "no research effort"!

Yes
I present to you, the Belphegor, a jet powered, crop-dusting, biplane. I think I need not say that this is a Soviet Bloc design, from Poland in particular.

Note the braces between the wings acted as tanks for whatever chemical agent it would be dispensing over the kolkhozy. It was not very successful due to a host of disadvantages, including:

Jet engines are not efficient at slow speeds, which are in turn required for crop dusting operations. The designers may have hoped to do away with this requirement by using it over the large collectivized farms of the USSR, but the straight wing attests to the top speed being low by design. The jet engine was apparently mandated by soviet planners wanting to simplify the logistics of fuel and maintenance by reusing the AI-25 engine.
Biplane configurations are less efficient than monowings of the same total area due to interference between both lifting surfaces.
For crop-dusting applications in particular, @Harper points out the fact that the shorter span of biplanes is detrimental to effective spraying, by limiting the width of the spray system, which needs to end short of the wingtips. Otherwise the agent will get picked up by the wingtip vortexes and spread in unintended directions.

On the other hand:

One advantage of biplanes is low roll inertia due to the shorter wings, which is mostly useful in dogfights and thus not highly-sought nowadays.
Another advantage of biplanes is the lower bending moment at the root of the individual wings, due to them being shorter. This allowed earlier designs to get into the air in spite of poor building materials and QA procedures; this solution was gradually abandoned as aircraft moved away from wood and fabric and towards aluminium alloys.
The lower span of biplanes might be useful in application that are span-limited, like modern airliners, which are limited by airport parking and runway restrictions. If you absolutely need to obtain more lift out of an airframe that is already at its maximum span, adding a second wing is not unreasonable.

Wow, I never knew a design like that existed! A jet on a crop-duster makes very little sense as you say, jets take much longer to spool up than props do.

The linked Wikipedia article says that's the world's only biplane.  Assuming that's correct it's the only answer (though I wonder about prototypes)

Yes, laughable.  Had seen this design a while ago, but it hadn't occurred to me this thus is actually a conversion from a surplus helicopter frame, which is even less fuel efficient!  More a garage project than a design from scratch, but practical if you have a lot of helicopters in your boneyard. Might have been a little better is they somehow got a turboprop on there.

@RobertDiGiovanni do you have a source on the helicopter conversion bit? Sounds weird because the wikipedia article does point to this being a clean(ish)-slate design.

@ChrisH The question is broad enough to allow for more answers that focus on the biplane pros and cons, and I'd myself appreciate if someone more familiar with this monstrosity would grace us with their knowledge.

No, but it did make me wonder how "spool up" issues were handled in modern jets and turboprops, along the lines of a constant speed, variable pitch jet! (or helicopter ?)  Anyways, it may have been a low budget "clean slate" from available parts.  So was the original U2, made with a Starfighter fuselage.  Could it have gone higher with a turboprop? Just got me thinking about adding fuel/air and increasing pitch of prop at the same time.  Not sure if a fan jet (or turbojet) can do that.

Unless you can identify the reused airframe components, I suggest you take it at face value. After all, this was not a prototype (which was a hodgepodge of parts, just like e.g. the F-117 prototypes), but underwent serial production. The only part that was clearly reused across the serial A/A seems to be the engine.

The short biplane wing works against cropdusters in a way.  In America at least, you are only allowed spray nozzles across 2/3 of the wing width, that is to keep chemicals out of the wingtip vortices where they will be kicked up and carried by the wind to places that should not be sprayed. Shortening the wing means more passes needed.

@GdD there are a couple advantages to using a jet engine; one of the biggest (and probably the reason this plane exists) is that turbines can run off of almost any fuel, unlike piston engines which generally run on a rather narrow range of fuels. If you're out in the country and don't know what fuel will be readily available, a jet might be a reasonable choice.

"Soviet in general, from Poland in particular"??? When and how did Poland get integrated into the USSR?

"Soviet", without the "Union" refers to a council of the type that Poland found itself under for nearly half a century.

@ChrisH: The world's only mass-produced jet biplane, technically.

@Skyler yeah, and on the collective farms the fuel most readily available would be the diesel for the farm machinery, which is very similar to Jet A.

@VladimirF Poland was integrated economically into the USSR post-WW2. This aircraft was designed and mostly built in Poland using Soviet engines and other equipment, to Soviet requirements, for use in the USSR.

@JimHorn No, no, just no. Simply no. It was used for such a broad sence (Al the power to the Soviets!) only for a short time after WWI for Germany, Hungary and extremely short lived Slovakian puppet statet ruled by Hungarians. After WWII the communist countries were not called Soviet countries. The adjectives soviet is only used for USSR stuff and that is true on both sides of the Iron courtain. Soviet Germany only refers to the shoet-lived thingaroynd 1919, never the GDR.

@Sean that's the suspicion I had, yes.

@RobertDiGiovanni The closest "related" designs were An-2 and An-14, used for prototyping. With 3000 planned units, conversion was out of the question. Jet was mandated to create fueling and maintenance synergy with other Ivchenko AI-25 powered planes. Helicopter look is merely a result of convergent evolution - when you put a jet/turboshaft on top of the cabin, you're bound to end up with something resembling a helicopter frame.

I changed the wording to Soviet Bloc, of which Poland most certainly was a part. I don't know what I expected, honestly, mentioning Poland has a habit of turning things into geopolitical discussions :)

Have to like the reliability and fuel use versatility of the jet.  And yes, they can be mounted on anything, including gliders (easier stowing) and biplanes (Screamin' Sasquatch).  Centrifugal jets may be a possibility for light sport aircraft, they powered the Mig 15.

@AEhere We call that period "communism". "soviet" is strictly limited to "USSR proper". Other Comecon countries called themselves "socialist" or "people's republic", but never "soviet".

A military jet-powered biplane was the I-153DM Chaika, which was adapted by strapping a couple of ramjets underneath each wing. (DM = Dopolnityelnyi Motor – supplementary engine).

picture source
The I-153 was a development of the Polikarpov I-15, an advanced fighter when it debuted in 1933. The I-153 sought various improvements, including retractable undercarriage, but even so by the start of WW2 it was no match for its opposition.
The Russians were pioneers in ramjet technology, and in December 1939 the designer I.A. Merkulov tested the addition of DM-2 and later DM-4 jets to a ski-equipped I-153.
There was little immediate advantage: the jets yielded only an extra 50kph at best. The disadvantage was that in standard flight the extra drag made the little plane rather slower. However, it is notable that this was the first ramjet powered flight.
Over 70 flights were completed with the I-153 variants. It is reported that Merkulov also tested the DM-4 in a similar configuration on the Borovkov-Florov I-207 biplane prototype. source

picture source

picture source

This is fascinating! I'd heard of  the Belphegor, but not this one - and it is neat to see ramjets combined with a radial propeller engine.

Technically the chaika could not propel itself on the jets alone, but that's beside the point. I'd heard of this thing but didn't register the fact that it was actually tested and that those were ramjets of all things. Nice one!

authors: Vladimir F Героям слава


text:
Why do GPS Copter Approaches require a slower final approach speed than conventional Copter Approaches?
AIM 10-1-2 says helicopter instrument approaches are designed with a maximum speed of 90 KIAS. However, it specifically exempts the final segment on GPS helicopter approaches, saying the maximum speed there is 70 KIAS. Here is the explanation in the AIM:

Obstruction clearance surfaces are based on the aircraft speed and have been designed on these approaches for 70 knots. If the helicopter is flown at higher speeds, it may fly outside of protected airspace.

Why are GPS copter approaches designed with a different obstacle clearance surface that requires a different airspeed on final? Also, if a helicopter flew faster forward with the same descent rate, wouldn't it get farther from the obstacle clearance surface (i.e. making faster speeds safer)?

Do the requirements, spell out a different Obstacle Clearance Surface?

Obstacle clearance surfaces are 3 dimensional. The traditional non-GPS approaches are designed around category-A aircraft[90KIAS] approach engineering and the routing options available from the nav equipment was more limiting than airspeed in many cases. GPS allows many new potential approach paths and 70kias helps take advantage of this routing reduced visual distance and turn radius while maintaining reaction time and buffer area.
From 8260.42

BACKGROUND. The foundation of these criteria are studies of GPS data from simulation
and flight tests. A significant difference exists between approach procedures to runways and
approach procedures to heliports. Approaches to runways terminate in relatively obstacle free
landing environments. Approaches to heliports commonly terminate in areas of dense obstacle
populations where executing a missed approach requires higher than average demands on pilot
reaction and performance. Speed limitations incorporated in these criteria take advantage of the
unique, slow speed capability of helicopters. These speed limitations allow construction of small
obstacle clearance areas and yield the lowest possible minimums.

Which is not a super satisfying answer, but probably the best you can expect from a 25-year-old standard set by now-retired un-named bureaucrats of a subgroup of an office of a department. I do know that GPS receivers were not trusted back then, and they were not augmented so subject to more signal error, and they calculated much slower introducing more inaccuracy. (Location updated once per second = 150ft at 90kts.) Many 70kt approaches can be flown by military at 90kts.


text:
How does gross weight affect helicopter autorotation?
The factors which affect helicopter autorotational aerodynamics include airspeed, gross weight, rotor RPM, and density altitude. The effects of these factors can be examined during a few phases of the autorotation, including entry, steady state descent, flare, and touchdown. The effects of gross weight seem very unintuitive to me, so I would like clarification on how gross weight affects the steady state descent and the flare, in particular.
Steady State Descent
My helicopter aerodynamics book says the following:

Gross weight determines RPM at a given collective pitch. At high gross weight, more blade pitch is required to maintain a desired RPM, so higher gross weight results in a slower rate of descent, assuming all other variables remain the same.

So high gross weight decreases descent rate. That's unintuitive to me, so I'm trying to build a logical path. I know from experience that making tight turns during an auto causes RPM to increase. Tight turns increase positive Gs on the aircraft, which is equivalent to increasing weight. So higher gross weight will tend to increase RPM, requiring the pilot to raise the collective (blade pitch) to maintain RPM. There's question 1: why does increasing weight (or G loading) tend to increase rotor RPM?
The second logical step is how this required increase in blade pitch will decrease the rate of descent. I understand that increased blade pitch increases AOA, thus increasing the lift produced by the rotors. However, this increased lift is opposed by the increased weight that started this whole discussion. Here's question 2: for a given increase in weight, is the resulting increase in lift larger? This seems to be the only way to achieve a lower rate of descent.
Flare and Touchdown
My helicopter's flight manual includes the following diagram, titled "Minimum Height for Safe Landing after Engine Failure"

This chart indicates that at a given density altitude, it is unsafe to be too heavy during an auto. I assume that the danger is related to the flare and touchdown, since during the descent it seems safer to have a lower rate of descent. My intuition tells me something about how the rotors store energy as RPM during the descent, and the flare and touchdown dissipate that energy in order to slow the helicopter's forward and vertical speed. It seems intuitive that a heavier helicopter will require more energy to slow, which means at and above some threshold weight, the helicopter will not be able to flare enough to touch down gently. But, is there a more rigorous explanation for high gross weight being dangerous at the "bottom" of the autorotation, i.e. how energy is stored and dissipated in the rotors?

With increased weight, the descent rate will indeed increase at the same collective input (the same main rotor blade pitch angle).  The rotor speed will increase as well as the upflow through the rotor increases.  I think your intuition is good with this, right?
Now, let's say you want to reduce the rotor speed back to what it was at the lower weight.  You'll need to increase collective, which slows the descent rate (and RPM) by increasing lift on the main rotor blades.  Once you are holding the original rotor speed, how do you know the descent rate will be smaller than the original descent rate?  This is a bit trickier to see, but one way to see it is to draw a diagram of an airfoil on a cross section of the main rotor from both the original (light weight) and new (heavier weight, same RPM) condition.
(I'll try to add a picture here later.)
You know the flow of air in the plane of the rotor is the same (same rotor speed) and the net torque is the same (still no engine power).  The magnitude of the drag is also about the same for a reasonable airfoil. What's different is the longer lift vector and the flow of air up through the rotor.  The only way for this longer lift vector to not accelerate the rotor (to a higher RPM), is for it to be "tilted up" slightly.  Since this lift vector is perpendicular to the new flow (and the RPM is the same), it's tilted up by decreasing the descent rate.

If you look at the situation in terms of power, an increase in weight (or any increase in loading) requires more power. As you don't have this power, the helicopter will descend faster, more air will go through the rotor leading to an increase in RPM. Hopefully this increase in RPM will provide enough lift to stabilize the vertical speed. Increasing the pitch to maintain the RPM within limits provides lift in a slightly more efficient manner so the vertical speed will be slightly reduced (compared to the situation of descending with the collective flat down and RPM screaming over the limit)
That said, I find the affirmation in your book very confusing. Maybe I'm missing something, but a heavier helicopter will descend faster than a lighter one under the same conditions. It needs more power to fly and the only way to get it is to descend faster. That makes landing more dangerous, because you have more vertical speed to offset during the flare and more weight to cushion before touchdown. If increased weight and increased rotor loading would provide lower descent speed I guess everybody would autorotate in fully loaded helicopter and doing tight turns all the way to the ground :)


text:
How to choose between BasicMed an a Class III Medical?
I'm due for a medical this year, and my last one was before the BasicMed program existed.
I'm a VFR PPL, flying small planes with 6 people or less.
Is there a clear reason to use Basic Med or Class III Medical?

Related

How long ago? Your most recent medical certificate must have expired after July 15, 2006, to be eligible for BasicMed. (10 years before the law was passed, not 10 years before the current date as many believe.)

I guess it depends on whether you intend to fly a larger aircraft at higher altitudes at faster speeds or one with a limited number of passengers at lower altitiudes and airspeeds.  If the latter is going to be the only flying you do, then a basic medical will be a good choice.  If you intende to undergo additional training and obtain additional certificates, ratings, or type ratings, I believe you will be required to hold at least a third class medical to do so.

FWIW, you can take a checkride with BasicMed; see the updated wording in 61.23. That might or might not be important, as you said.

I don’t know that for sure.  It may well be that the FARs have recently been updated to include this. But the current 2018 FAR states that you need at least a third class Medical to apply for a certificate or a rating.  I talked with the medical certification division in OKC and they thought one could apply for a certificate with a basic med but wasn’t totally sure.  I’ll have to ask a DPE in the field to see if they’re cleared by OKC to accept a basic med from an applicant for a checkride.

I'm not sure what source you mean by "the current 2018 FAR" but if you look at 61.23 on ecfr.gov the text in 61.23(a)(3) allows using BasicMed as an exception to a third-class medical for a checkride. I've answered your other question anyway, hopefully it's helpful.

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text:
Is a recoil start (hand propping) allowed if it isn't mentioned in the aircraft manual?
Is a recoil start (hand propping) allowed without it being referenced in the aircraft manual? In a Cessna 150, for example.

Actually this is pretty commonplace, its called "hand propping".

That always looked so crazy dangerous to me. I don't think you could talk me into doing that. As clumsy as I am I'd surely fall into the prop or not get my hand out fast enough.

Yeah, it's the airplane equivalent of pushing your car down a hill and then jumping in to pop the clutch before it gets going too fast.  What legal system?

That is not a “recoil” start, because there is no coil to pull. It is simply manual start.

@RyanMortensen, note that most car manuals now say to never do this (connect external power instead). Most aircraft engines are comparably ancient though and shouldn't have the kind of problems with this the new car engines do.

Allowed according to what?

You didn't say exactly what "allowed" means, e.g. do you mean approved by the manufacturer, or legal in a certain country? But if you're asking is it legal in the US (under FAA regulations), then the answer is yes.
AOPA has a nice article on exactly this question, called Hand propping: A legal primer. It says:

There is no specific FAA regulation that applies to hand propping an
  airplane, either to prohibit it or to direct how it is to be done

But:

The FAA contends that hand propping is a two-person operation and has
  expressed this view in the Airplane Flying Handbook (FAA-H-8083-3A)
  under the section titled “Hand propping.” Of course, this publication
  is not regulatory, but the NTSB was surely influenced by it in a 1983
  legal decision. In that case, the FAA sought to suspend a pilot’s
  certificate for being careless or reckless when, while attempting to
  start a VariEze experimental aircraft, it “got away” and ran into a
  parked aircraft.

The NTSB concluded that the pilot had violated 14 CFR 91.13 (careless and reckless operation):

The board affirmed the administrative law judge’s finding that there
  had been a 91.10 (now 91.13) violation

That means that hand propping itself isn't illegal, but doing it wrongly and against the FAA's general procedures could get you in trouble:

There have been at least two previously issued NTSB (full board)
  decisions and one subsequent decision that refer to these generally
  accepted procedures and precautions for hand propping. The precedent
  has been set. So, hand proppers beware; if you fail to follow proper
  precautions and the airplane gets away, the FAA might pursue action
  against you for being careless or reckless.

That was exactly what I needed! I know a flight instructor who has a course about execution of hand propping, but i've tought that it would depends on the aircraft manual or something. A starter problem could be very dangerous, because hand prooping would bypass the starter problem, and if an engine fails in-flight, you would not be able to restart it, unless the engine is "ram air driven".

Unless an operation is prohibited by regulation, the laws of physics, or the limitations section of the POH/AFM, it's not illegal.  It might be stupid, but it's not illegal.
There is an important distinction to be made here.  The manufacturer can state that hand propping "is not recommended" but that is not a binding statement and hand propping is still permitted...though not recommended.  Simply because a procedure is not recommended does not mean it's prohibited.  Now, if the manufacturer places a limitation of "no hand propping" in the limitations section (the real, formal section of the POH called "Limitations"), then the procedure is not authorized at all.
I know of no airplane with this limitation because it's not really a problem.  I think our good friends physics and Darwin take care of that for us.  I've never seen a person hand prop a GTSIO-520 (physics) but if someone manages to hand prop a large piston engine I doubt we'll ever hear about it (Darwin).
Smaller piston engines are actually easy to hand prop.  Hand propping of O-170s (Continental A series) and O-190s (Continental C series) is actually quite common because many of the airplanes equipped with these engines lack electrical systems to power starters.  The C-150 uses a Lycoming O-200 which is only 10 cubic inches larger than the Continental O-190s.  The O-200 is rarely hand propped, however, because the aircraft that use it generally have electrical systems and starters.  Why hand prop when you can just use a key?

Why hand prop when you can just use a key?
Insufficient battery charge, that would be recharged with the alternator later.

Then you wouldn't be able to use a key.

When I was flying skydivers we had occasion to hand prop a Cessna 182. That's almost a 500 cubic inch engine, and hand propping it is definitely NOT in the manual. But all reciprocating aircraft engines have impulse-coupled magnetos, so you don't really have to turn them quickly to get them to fire. When you move the propeller through the sweet spot, the mag will unwind and cause a spark.  The coupling makes a ticking noise that you can hear. If there's fuel in the jug when the magneto fires it will kick, and that's usually enough to start it.

While you explain that it can be done even on a C182, you don't say anything about whether it's allowed, which is the question.

all_licenses: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/3.0/


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How should simulator time be logged in a pilot logbook?
In a full motion Level C or D simulator like those used by the airlines and for jet type ratings:

How should a pilot log the simulator time in their logbook?  I.e. Can you log:

Total Time
Instrument Time
Time in Type
Cross Country Time
Night Time
Landings (including night landings)
Dual given/received
Anything else?

It's not an answer to your question, as you've tagged it as FAA repated, but maybe nice to know and still helpfull: In EASA logbooks there is an extra culum for so called synthetic trainig devices, where we log our time in any kind of approved simulator. There is no difference between FNPT or full flight. This time is completely independent of the other flight times, but can still be used to stay current on type if the hours are loged in a full flight.

I always logged it as simulator time. Though those high level sims are as realistic as the actual aircraft they model.

@Shawn That they are.  I know that some of the others are allowed too but not sure on all of them!

You log simulated instrument time in an FFS, Full Flight Simulator.
The relevant FAR's are 61.4, 61.1(b)6.

https://www.flyingd.net/documents/LOGGINGSIMULATORTIMEcopy.pdf
This link provides good information of logging simulator time.
I copied and pasted the article below.

LOGGING SIMULATOR TIME One thing that generates more questions than
  anything else (besides FAA certification) is the proper way to log
  training time on an ATD. Here's a basic framework: In the "N" number
  column, put the type/model of simulator. This lets an examiner know
  the simulator is a BATD or an AATD (Advanced Aviation Training Device)
  and is eligible for the time towards a certificate or rating. It's
  also a good idea to provide a current copy of the LOA to clients to
  show to the examiner.
In the "Type" column: Record the actual aircraft make/model flown in
  the simulator (TAKEWING’S IS A C182RG). This is required information
  as some examiners only allow multi-engine AATD time to count towards a
  commercial ticket if flying in a multi-engine aircraft.
In the "To" and "From" columns: Record the airports used during
  training (77S etc.).
The "SEL," "MEL," "Day/Night" and "Cross-Country" columns should
  remain blank. These columns are designated for actual aircraft flight
  only. Similarly, do not log landings (i.e. 90-day day/night landing
  currency cannot be performed in an AATD).
In the "Approach" column: Log the number of approaches performed in
  the simulator. The criteria for an approach is the same as in an
  aircraft, passing the FAF in IMC and breaking out at or above DA/MDA
  with a subsequent landing or executed missed approach.
In the actual IMC Column: No time is logged.
In simulated IMC (hood or IMC in an ATD): Log the actual time in IMC.
  For example, in a 1.8 hour session, it might be typical to log about
  1.5 hours of simulated IMC.  In the "FTD" or "Flight Simulator" column, log the total time in the ATD.
In the "PIC" and "Total Flight" columns: log all time as this shows
  the pilot experience time. An examiner can see the time under
  "SEL/MEL" for actual aircraft time and the time under "FTD" or "Flight
  Simulator" for simulator time. The combination of both of these is the
  pilot experience. In the "Dual" column, log the entire dual training
  time in the ATD.
Adhering to these guidelines should insure full credit for valid
  training hours in an ATD.

This all sounds reasonable, except that in the simulators that I refer to you are allowed to log landings, and the visuals can be set to day/night so I believe, but am not sure, that you can log night time as well.

@Lnafziger faa form 8710-1 has the logged-time matrix generally relevent to legal logging requirements (As opposed to the requirements of specific operations like a 141 program), then add to this the specific needs of currency, like approaches. ATD is only good for logging total sim time, dual received, and instrument approaches. FTD time can be logged as night PIC, and full flight sims can also log night takeoffs and landings. Single engine or multi engine configuration should be noted and the types tallied separately (land or sea is irrelevant for sim logging) for 6 totals SE/ME*ATD/FTD/FFS


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Why is it not a good idea to climb higher than a level at which you would have a cruise weight-climb speed less than 500 ft/min?
In relation with What is weight-climb speed?, why is it not a good idea to climb higher than a level at which you would have a cruise weight-climb speed less than 500 ft/min?

Because ATC expects you to climb with at least 500 fpm when crossing to the next level. Otherwise you will block intermediate levels for an extended period of time.
If you are climbing 2000ft to the next available level for your direction of travel, that will take at most 4 minutes at 500fpm or more. This means the flight level you are crossing will need to be free of traffic from the opposite direction for four minutes to ensure legal separation is maintained. If you climb slower, ATC can't properly accomodate your climb.

Presumably, maneuverability in a TCAS situation would be an issue as well.


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What are endplates? How do they work?
Winglets have been discussed fairly regularly, but not much can be found on the topic of endplates. What are endplates, how do they work, and how do they relate to winglets?

The air doesn't notice or care that we humans use so many different names for those wingtip extensions. They all help to keep the pressure difference up between both sides of the tip and add some friction drag.
Since giving basically the same thing such a variety of names is a pettifoggery and there is no standardization for naming them, it is hard to give a clear, distinguishing feature. If I now say that endplates extend to both sides of the wing and are smaller, while winglets point up only and are larger, I am sure that somebody will rightfully point out an exception to this rule. Just look at the latest monstrosity Boeing added to their new 737NG.

Boeing scimitar winglets (picture source)
When the term endplate is used, the transition between wing and extension is sudden and sharp, while winglets tend to have a smooth, rounded transition. Maybe this would be a better guide, but also here exceptions can be found.

Monstrosity? I quite like them. Like go faster stripes

@JonStory: De gustibus et coloribus non est disputandum.


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What was the commercial speed of Concorde?
I work on time-space cartography in a historical perspective and need to establish a commercial speed of Concorde aircraft flights based on timetable data. This issue differs from the issue of the maximum speed of planes, because in a time geography perspective I want to consider speed from the point of view of the user, the traveller, i.e timetable commercial speed, and not maximum aircraft speed.
I found some indicative timetables of London-New York in 3,5 hours for 5 850 km which turns into an approximate value of 1 600 km/h. Could anyone confirm these data and this figure?
A related problem is that time-tables are not symmetric, because of trade winds, so that transatlantic routes take longer from Europe to USA that the contrary. I want to use the longest value since it provides a consistent value for minimum time-distance.

As an example, here's a query about timetables: http://www.airliners.net/aviation-forums/general_aviation/read.main/3820978/  note some more research will be needed to establish if these are airborne times, or include taxi etc.

Another example of timetable info:  http://forums.flightsimlabs.com/index.php?/topic/4874-complete-list-of-concorde-scheduled-flights/

Thanks a lot Andy this solves my question. I have been calculating commercial flight time from these data and it is a surprise that they do not differ so much 3h45 eastward and 3h45 (AF) or 3h55 (BA) westward. So I have my figure: 5850 km / 3h45 = 1 560 km/h

Note that those are usually the timetabled examples. In reality most flights don't arrive on time...

Given the currents answers, you may provide the difference between cruise speed (speed during cruise phase) and commercial speed (average speed for the whole travel, taking into account all steps and stop)

My problem is not commenting on the difference between cruise speed and commercial speed (Manu H), or if commercial speed is accurate or respected (Jon Story), it is just converting timetables into commercial speed, a speed perceived and lived by travellers regardless of the top speed of the transport mean.

This answer deals with operational speed but do not talk of commercial speed which is based on timetables and communicating to customers when they book their flight. So this answer, despite being interesting and accurate, does not reply to my question.

The Concorde's cruising altitude was 56 kilofeet; tradewinds are only found in the troposphere, which barely reaches 56 kft at the equator and tops out (sometimes much) lower than that at nonzero latitudes.

I want to measure a commercial speed for Concorde flights. The answer was given by Andy in his comments providing links to websites that recorded past timetables for Concorde: forums.flightsimlabs.com and  www.airliners.net
Timetable schedule must take into account time difference between cities so that a British Airways Concorde flight JFK 12h15 to LHR 21h00 with -5 hours difference will give a 3h45 of commercial flight duration. Surprisingly, to me at least, trade winds did not seem to play a significant role in this measurement because timetable on the reverse route exhibit similar duration. Air France flights follow the same rationale. The measurement indicate a general figure of 3h45 for transatlantic Concorde flights.
Next step is determining the kilometre distance. As I want a geographical time-distance I care only about great circle distance and do not care about the exact path followed by the flight which would tell about aircraft/pilot/airline performance. I used the  flightaware.com website. My only issue is measuring the performance (speed) of the transport system in getting from point A to point B.
So I finally have my figure: 5 850 km / 3h45 = 1 560 km/h was the commercial speed of Concorde (or 969 mph in non international units).

The Concorde cruised at 1350mph (~Mach 2.05 at 55,000Ft.)
Concorde’s fastest transatlantic crossing was on 7 February 1996 when it completed the New York to London flight in 2 hours 52 minutes and 59 seconds.
When it flew the average flight time (was) around 3 hours 30 minutes, but can be slightly longer if the aircraft (needed) to hold before landing at the local airports.
Wind is a huge factor in flying. A headwind or tail wind can mean a big difference in flight time. The Concorde cruised at a significantly higher altitude than most airplanes ~55,000Ft. which means it was subject to very different wind than its sub sonic lower flying counterparts. At that altitude winds in excess of 100Kt are common place. So you could see a 200Kt difference in speed depending on direction.
Also of note the speed was often called out using Mach's Number (the Concorde flew a bit over Mach 2). However since Mach's number accounts for air density,  Mach 1 at 55,000Ft. is 660MPH which is significantly lower than the often quoted Mach 1 = 760MPH (which is the speed of sound at sea level).
One of the best sources of info on flying the Concorde is this podcast interviewing one of the pilots.

Are these flight times measured jet way-to-jet way, wheels off the ground to wheels on the ground or what?

The sources don't specify but the FAA defines time-in-services as wheels up to touch down but I'm not sure how they recorded the times here. From a passenger standpoint gate to gate is usually what people care about.

Mach's number accounts for air density just to be pedantic, it's outside air temperature that needs to be accounted for, not pressure.

+1 as the podcast Dave linked to is very relevant - it includes comments on the wind speeds at high altitude (surprisingly low to me) and the very short time spent circling at the end of the journey (due to fuel efficiency).

Timetables tend to confirm the lack of trade winds for Concorde most probably because of its flying altitude

@theworldisnotflat Relevant wikipedia entry, according to which Concorde indeed flew above trade winds altitude.

Well, this is very dependent on the windspeeds for a local area which changes day by day. The official "Cruise speed" for Concorde is 2140 kph. Other than that, your question is way too broad because the "relative airspeed" varies by day and time of day as well as location.

When I flew on it in 2000, the Mach meter at the front of the passenger cabin varied from 1.99 to 2.01

Mach is a function of temperature, so I would not take it as indicative, for the purpose of this question.

As someone who flies has flown transcontinentally on various aircraft a number of times a year for 15 years, I can tell you that the actual flight time varies greatly. It can take as little as 4.5 hours eastbound in the winter, and over 6 hours westbound. The only constant is that the planes regularly fly at .80-.84 mach.


text:
Why is dropping off passengers on the ramp by bus not more common?
Even at remote terminals as discussed in this answer it seems there's a preference for using a jet bridge to get passengers to and from the aircraft.

Can't the passengers just be bussed directly to the aircraft rather than the remote terminals?
Why the use of a jet bridge here if they can use stairs at other times?

I've made a few edits to your question for clarity. Let me know if you think I butchered the intent.

They can, it's just that they aren't (usually). Subtle difference.

What happens when its raining or snowing? You have to walk up the stairs and wait in a line while getting soaked?

Passengers can be bused directly to the aircraft. They climb stairs directly at the aircraft door. This is common at many airports with remote stands (and sometimes even adjacent to the terminal when boarding small aircraft used for regional flights). The bus to jetbridge situation shown here is unusual.

I've taken a bus to an aircraft, stepped off, walked three steps, and climbed stairs to the aircraft door. Multiple times.

@RonBeyer Pretty much. Or use an umbrella or hood. I've seen stairs at some airports that are covered, so you wouldn't get wet on the stairs if they had those.

i only want to board something once

Not sure why you consider it uncommon. Many many airports around the world drop people off by bus, for example Madrid, Frankfurt, Dubai, Istanbul to name a few larger ones. Other airports like Kathmandu (Nepal), Marrakesh (Morocco) or Kangerlussuaq (Greenland) you walk directly from the gate to the plane. It's also becoming more and more common (in Europe) to board the aircraft from both front and back to speed up boarding on commute flights, often done by having the passengers leave the jet bridge, and walking on the tarmac to the plane.

Voting to close because the question seems to be based on the misconception that it's rare to drop passengers off on the ramp by bus. In fact, it's extremely common and overwhelmingly more common than the arrangement described in the question.

The use of a jet bridge has several major advantages over loading passengers from the ramp via portable staircases or built-in "air stairs", among them:

Boarding of handicapped passengers
Not all passengers can use stairs: a jet bridge allows passengers with limited mobility, particularly those confined to wheelchairs, to board and disembark from the same level as the passenger deck.
Accommodating these passengers from the ramp would require some kind of lift mechanism to raise them to the passenger deck of the aircraft - this is typically accomplished elsewhere in the terminal when a jet bridge is used, e.g. via passenger elevators in the ticketing area, or in the type of design shown in your question, via an elevator in each "mini-terminal".
Passenger shelter
Boarding from the ramp may work well on a beautiful spring day, but in less favorable conditions (rain, snow, temperature extremes) most passengers would not find the experience to be enjoyable. The jet bridge provides an enclosed and relatively climate-controlled route from the terminal to the aircraft.
Passenger Safety
Airport ramps are inherently dangerous places: Aircraft are starting their engines, being pushed back for departure, etc. and ground support vehicles are moving at all times carrying luggage, cargo, catering supplies, etc. to and from the aircraft. In addition to the ongoing movement there is a great deal of noise from these operations.
Bringing passengers into this environment represents an inherent liability risk: Someone could be struck by a support vehicle, or injured by jet blast. A jet bridge is an enclosed area away from these dangers, providing an improvement in passenger safety.
Airport Security
A great deal of effort goes into ensuring that unauthorized persons do not have access to the airside facilities at an airport. Bringing passengers into this area represents a security risk, as even a ticketed passenger could be intent on causing disruption or damage once airside.
A passenger wandering off on the ramp would represent both a safety hazard (as the passenger could be injured) and a security hazard (as the passenger could perform any number of malicious acts before they are located).

Regarding safety: often the stairs are a fairly flimsy construction and sometimes I have seen them going dangerously close to oscillation, either from wind blowing or from passengers climbing them in just the right frequency. Not the nicest feeling when you stand on top and watch the gap...

Another point in this field could be: you need to handle yet ANOTHER set of vehicles. You have enough things going on between luggage, catering, maintenance... . And now you add several buses, plus stairway-vehicles, plus whatever is needed to take the crew to the plane.

One thing to note is that the example posted by the OP is not a traditional Ramp boarding scenario - it uses fixed jet bridges on the ramp, and is essentially a gate+jet bridge that you access via a bus. This negates your first point entirely, and a good deal of the second. The third and fourth are pretty much negated too, as there's no "walking around the aircraft" - you get off the bus, straight into the gate.

@JonStory The question as I understood it was Why are they using a remote gate & jet bridge and not boarding directly from the ramp? -- The answer to that "why" are the points I raised: Bussing them to a remote gate allows an elevator in the remote gate to be used to get handicapped passengers up to the boarding level, keeps them out of the weather, and avoids having them loose on the ramp where they could harm themselves or an aircraft. The points aren't "negated", they're the very reason those structures exist.

@JonStory I don't see any of the 4 points failing even for a bus-operated jet bridge.

@yo' they would hold for something like the mobile lounge too, though one of the implied benefits (fewer vehicles driving around airside) would be lost.

@voretaq7 When I saw the thing, I knew that you don't want something this heavy and this complicated and purely on wheels so close to your precious airframe :)

@yo' It's really just a variation on the catering trucks - you're counting on the driver (and the operator in the top part operating the accordion bridge part) not scratching up your shiny new paint job.

Add to your 4 reasons that airlines try to optimize the time boarding and leaving the airplane for economical reasons. Time is (a lot of) money (when an airplane is not flying).

Instead of built-in "air stairs" or portable staircases, Mobile lounge have been used for several airports to transfer passenger from terminal to planes directly.

Plane-Mate in Washington Dulles airport (Creditor)

However for several reasons most of the mobile lounge has been replaced.

Rise of air transport: Number of flights and capacity of airliners has benn rising quickly in these decades. It require more mobile lounges to serve the passengers. Furthermore the road network within airport have to be upgraded if there are too many mobile lounges. Transferring passengers by People mover or walkway is cheaper and faster.
Trend of airport operation: Since airport security has been continuously rising in these decades, tourists stay much longer in the airport than before. Hence, airport operator are likely to create more retail area so that they can generate more income. The concept of airport lounge does not fit this trend.

Though mobile lounge has been kicked by Jet bridge, it is still used for many airports for special customers, eg: wheelchair tourists to airliners in remote stand.

An additional complication not touched in the existing answers is the disparity in number of passengers that can be handled by an airliner and a bus.
A large bus might be able to accomodate somewhere on the order of 50-100 passengers comfortably while maintaining a reasonable turning radius and maneuverability as well as reasonable boarding and unboarding times, assuming luggage remains handled separately.
Large aircraft can handle far more passengers than that. For example, an Airbus A380 can take 853 passengers, and a Boeing 767 can accomodate up to 375 persons. Even the MD-80 can seat up to 172 passengers.
This means that you would need anywhere between four and seventeen bus roundtrips to get everybody onto the plane (two for a big bus and a MD-80), as opposed to simply moving everybody through a single jet bridge at the gate. Intuitively, this would seem to take far longer, in turn reducing aircraft turnaround and thus driving costs up. While the time to board passengers can still be used productively, I find it doubtful that the same could be said if the time to board passengers was at least several times longer.
For aircraft up to the number of passengers that can comfortably be accomodated by a single bus roundtrip, other issues (security, etc.) notwithstanding, boarding by bus remains a possibility without significantly impacting turnaround. But those types of aircraft tend to not be used for anything but short haul flights anyway.

And the same 4-17 roundtrips to get everyone from the plane back to the terminal upon landing.

This is a good point, but it also exists for remote gates like the ones shown in the question: Multiple busses will be required to bring a planeload of passengers to and from the remote gate. The advantage to the remote gates rather than bussing directly to the plane is that the busses are not all trying to move on the ramp - they have their own road. If passenger volume makes bussing impractical a local light rail loop could also be used to serve the same purpose.

I'm pretty sure that nowhere boards A380s in all-cattle configurations by bus at a remote stand. So that part just isn't relevant.

As far as I know, Dubai and Frankfurt uses jet-bridges exclusively for the A380, but for the Boing 777 Dubai often boards all-cattle configurations by bus. It took me a 12 minute bus-ride just to get from/to the gate in Dubai (B777 from/to Stockholm)

Most articulated buses can probably get around 60-70 people maximum, and even then, people will be bringing fairly large bags with them, their luggage which can make that number even smaller.

The other answers address the question of why dropping passengers off on the apron by bus isn't common, but it does happen - mostly at smaller airports (for rural places with perhaps just one gate) and even at large busy hubs.
There are several reasons airlines sometimes board by having passengers walk to the plane and then either up a ramp or airstair:

Not enough gate space.  This could be because a flight that should have left is under some delay and taking up a gate, an inbound flight is early, a diverted aircraft has arrived, or there are simply too many scheduled flights right now.  For example, if a terminal was originally built to accommodate 10 certain size  aircraft but the airline expands its fleet to use a larger aircraft, such that the terminal can now serve only 9 at a time, they might occasionally or routinely bus passengers to and from that 10th flight.  This could also be a temporary situation lasting hours to months, caused by terminal construction for example.
Plane too small for a jetbridge.  This is the case with some smaller turboprop or jet planes in use by airlines.
Other unique situations.  For example, at LAX, customs in most terminals close after a certain time of day.  An arrival from Mexico to T7 at night will involve parking at T7 and the entire passenger group and flight crew getting on large busses and taken to customs at the main international terminal.

Could also airport costs billed to the airline company play the role? I mean, if there is something like lower cost for using a bus vs. higher cost for using a jet bridge. I do not have access to these prices, I am only thinking.

@miroxlav definitely.  Most airlines don't own busses or retain drivers, so that could be provided by the port authority or a third party, but someone has to pay for it.  The airline might exclusively rent a number of gates, but then be able to on short notice use other gates for additional fees, or they might choose a hardstand and bus.  It's a choice made by either local or national operations depending on the company.


text:
Do modern aircraft still have mechanical sensors as backup to GPS?
A comment here Why does "no aircraft cross directly over the pole"? indicates that modern aircraft use GPS for navigational purposes, which makes perfect sense.  However, do these aircraft also have backup mechanical sensors (altimiter, magnetic compass, etc.) in case GPS signals go haywire or are not available?

Clarification might be helpful. GPS is a system for precision location determination. Are you asking if there are backup precision navigation instruments (e.g the use of terrestrial navigation radials or the presence of onboard inertial measurement systems) ? An altimeter, magnetic compass and airspeed indicator are not precision navigation instruments, they are primary flight instruments.

Note that GPS is not used for measuring altitude except for the terrain proximity warning. This is because barometric altitude and altitude are different quantities, but all aircraft must agree on one, which is the barometric one.

@tillmas, I was primarily wondering about primary flight instrument backup capabilities in case the primary precision electronics-based instruments became inoperative.  Essentially redundancy in general navigation function by two completely differently-designed systems.

@ScottEvans, then I think your question should be edited to say that.  You should also understand that primary flight instruments are not backups to GPS.  GPS is not a primary flight instrument, it is a navigational instrument.

In light aircraft they typically do: Glass-Panel aircraft will also have traditional "steam gauge" backup instruments of some kind.

Note the airspeed indicator, attitude indicator, and altimeter to the left of the pilot's PFD.
This is however no longer guaranteed: A completely independent electronic backup system with its own power source may be used in place of the traditional "steam gauges".
This can be seen on new Cirrus aircraft, which have digital standby instruments (in the green box):

Similarly transport category jets may have traditional backup instruments:

Or they may have an electronic backup system:

Note that the electronic instruments in these cases aren't GPS-referenced: They are gyroscopic instruments with pitot and static input for airspeed and altitude/vertical speed calculation.

The question appears to be asking about backup for navigation systems, not flight instruments.

Basic VOR navigation equipment (and sometimes NDB or DME aswell), altimeter and magentic compas are mandatory equipment for any IFR aircraft
It's a pretty safe bet any aircraft will have them onboard.
Also, a good side story to tell is that mechanical sensors do not act as backup to GPS: in case of altitude the 'mechanical' baro-altimeter is still the primary instrument, as for navigation the radios & IRS are still used to enhance the estimated GPS position

There's no requirement in the US to have a VOR receiver; the regulation only says "navigation equipment suitable for the route to be flown".

Yeah, the FAR is surprisingly vague about this, whereas the ICAO (and EASA) make this a little bit easy: check EU OPS 1.865 d) (1)  (at least 1 VOR , or 2 if it is the sole means of navigation) ... FAR maybe has an equivalent I'm just not so familiar with FAR


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Would an aviation engineering background be helpful for a Flight Data Monitoring Analyst?
I am working now in the aviation sector and I am technical administrator for planning aircraft maintenance events. Recently I search for new opportunities and found "Flight Data Monitoring Analyst"? Could someone tell me should I have an aviation engineering background to qualify this job?
In their job description, candidates need to have bachelor degree and experience working in the aviation sector.

Welcome to Aviation.SE! It would be useful if you could post more information such as the actual job description. You could also just try applying to the jobs or messaging the company advertising them, the worst that will say is "go away" or just ignore you.

If I understand correctly, you want to know if you specifically need an aviation engineering background rather than just general aviation background?

I wonder as a FDR analyst, should I know how to read the aircraft attitude, speed and height etc. I tried to google more info about Flight Data Monitoring but what I found it is mostly about Flight Data.

Today's aircraft record many parameters, some are even sent live to headquarters. Besides accident investigation, these data can be analyzed to identify patterns, trends etc for improvements in safety, efficiency, economy etc. It'd help if you already has an understanding of various aviation concepts, but I don't think aviation engineering or pilot experience is necessary (although it'd certainly help).

Skybrary's page on Flight Data Monitoring defines Flight Data Analysis:

Flight Data Analysis is founded on Operational Flight Data Monitoring (OFDM) which in North America has become known as Flight Operations Quality Assurance (FOQA). It is a process which routinely captures and analyses recorder data in order to improve the safety of flight operations.
Flight Data Analysis. A process of analysing recorded flight data in order to improve the safety of flight operations. (ICAO Annex 6 - Operation of aircraft)
Operational Flight Data Monitoring (OFDM) is the pro-active use of recorded flight data from routine operations to improve aviation safety.

So, this position would be focused on analyzing data from the flight data recorders to make sure the aircraft are being flown in safe and efficient manner.
Engineering (both in aviation and in general) is concerned with design. While an aviation engineering background would probably provide some useful insights, it normally isn't necessary for a position that is not concerned with designing aircraft or aircraft systems.
It would seem that piloting knowledge would be more necessary here than engineering knowledge. In order to analyze whether flight operations are being conducted safely and efficiently, you first need to know what constitutes safe and efficient flight. Technical knowledge of aircraft systems would certainly be needed, but probably more on a pilot level than an engineer level. Additionally, statistical analysis experience will almost certainly be needed.
As an example, here are the qualifications listed for a Flight Data Management Analyst position that I found in a search:

Essential skills and qualifications:

Experience in statistical analysis and preparation of graphical representation of data
Hold accreditation as an aircraft accident/incident investigator or equivalent
Hold accreditation as quality auditor or equivalent

Desirable skills and qualifications:

Experience as a pilot
Sound aviation technical knowledge in Flying Operations, or equivalent
  Experience in analysis of flight data, using flight data analysis systems (e.g. ADI, Aerobytes, AirFase)
Experience in utilisation of flight simulator software to recreate flight events
Familiarity with current EASA regulatory legislation
Experience in undertaking investigations


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Does a 40 years clean crashes sheet of airliner makes people fear to fly with them because there is bigger pressure on the company?
I am planning for my 2nd flight.
The first flight was in November 2017 from Beirut to Istanbul which took 1h45min. I asked this question on this site, explaining my Phobia to professionals on the site.
The flight was good enough, but the crew was rude, the safety guidance was in Turkish though 90% of passengers were English and French speaking Lebanese. I couldn't understand anything, so I was concentrating on their hand movements to understand what they are saying and trying to catch a few things. The pilots were speaking to us several time during the flight in Turkish and even the hostess weren't reacting to what the captain is saying. So it was a little bit confusing.
I was calmed down, maybe because of the Xanax 2.5 mg that I already took before take-off.
Now I am preparing for my next flight next week to Paris on another Airliner. I don't know if I am allowed to mention the name of the airlines, but it have a really great reputation. I was searching in this wikipedia link on crashes related to the airline and the last one was in 1976 due to a terrorist attack. More info in this link.
I know the following may not be logical for most of you:
My problem now is that the huge clean sheet of the airline company makes me more scared to fly with them. If an airline didn't have any crash since 40 years, is it good to fly with ? Does that add pressure on companies responsible and pilots and even flight engineers which may make mistakes concluding to crashes or problems ? The flight time is 4h40min, and that adds more pressure on me and considering 90% canceling my flight.

You'll be absolutely fine. They have a clean sheet because they know how to properly operate an airline. Statistically, once you board the airplane, the safest part of the journey starts. So while your fear is real, it is irrational. I would recommend taking a nervous flyer course, so that you will know better what to expect and will not be thrown off by completely normal things. And whatever you do, don't cancel your flight. The best way to get over any irrational fear is exposure.

@Sanchises thank you. Yeah. I've been told that after my first flight, the things will better in the next ones. Apparently for me, the phobia is increasing in my second flight especially after the 2 crashes in Russia and Iran which conducted to killing all passengers on the both flights.

Don't forget there are over ten thousand flights in the air at any given moment. Per hour, it's four times safer than driving a car. Per kilometre, it's sixty times safer than driving a car.

A good safety record means that the airline spends time training their pilots, maintaining their airplanes and fostering a safety culture. Logically it should make you feel safe. However, when you have a phobia your brain's normal logic doesn't apply, I recommend you get some cognitive therapy on this issue to help you move on.

You'll be fine.

Thanks Zeta-band for those 3 words. You really really make me better. Thanks all guys.

Your question looks like it's more about statistics than anything else.
It's a common misconception to think that in a random lottery where event E has X% chance of happening, if there is N draws without any occurence of E, E is more likely to happen.
This is completely wrong.
If you flip a coin, you have 50% (X) chances of getting heads (E).
If you flip it 5 times (N) and get 5 Heads, you don't have "more chances" to get tails on your 6th draw.
In other word, se sequence Heads Heads Heads Heads Heads Heads is as likely as the sequence Heads Heads Heads Heads Heads Tails.
As for your flight, all airlines authorized to fly into EU are considered safe, and any difference in safety record is a rounding error, and statistically insignificant.
You can read more about this misconception on wikipedia Gambler's fallacy
Have a nice flight.
PS: For the safety instructions, please refer to the pamphlet provided at your seat, it contains all, if not more information about the presentation.

Thanks a lot. I get your point. By the way, the pamphlet provided was in Turkish too, so that was disappointing :(

@droidnation all Pamphlets are more or less the same (except emergency exit locations). You can look up one in your native language. If you want the exact pamphlet as the plane your are flying, please ask a new question; including either the flight number or if you know it, the aircraft type your are going to fly with.

I will ask about it. Thanks. What make my phobia increased in the last few days is because hearing about 2 airplane crashes in Russia and Iran which led to more than 130 fatalities. The year started too bad for the aviation. last year the fatalities was less than 100 persons. We still in March and we have more than 100. That make me more nervous.

@droidnation The cards are designed such that they can be understood be illiterate people. You won't miss any important information if you can read the pictures.

@droidnation You're reiterating the Gambler's fallacy. Those incidents just coincidentally happened close to each other in time.

Air crews don't think about their past safety record because they know that it could change with the next flight. That might not be the most comforting thing for you to hear but you know it's true - it's extremely rare, but planes can crash if the wrong actions are made.
But this is the mindset that makes an airline safe. Some people with a fear of flying believe that only they think about what could go wrong with the plane, but that's not true. Crews and management spend a lot of time thinking about what can go wrong, so that they can take action to prevent that scenario from happening. An example of this is that before every single flight the pilots will discuss the takeoff path and what they will do in an emergency, eg "if an engine fails below 2000ft we won't be able to climb over that mountain, so we will turn right to avoid it, and keep climbing until at least 6000ft". Aircraft designers and engineers have a similar mindset, so lots of redundancy is built into everything they do. Management think about all of the ways a pilot might make a mistake, so designs specific training programs to help prevent them, as well as mandating special procedures to be followed.
If an airline has been flying for 40 years since its last accident, it is probable that they have a good culture of thinking about what could go wrong on the next flight. You as a passenger don't need to think about any of that though. You just need to think about what meals you're going to have in Paris.

I don't know if this might help or not, but I suggest viewing FlightRadar24.com. This will help you visualise just how many aircraft are flying around the world at any point, and that last year not a single commercial jet crashed. It's quite amazing just how safe flying in a plane is.
Secondly, you can also watch airline safety videos on youtube. They all contain the same basic information, but each aircraft and airline has a specific video which you should watch on your flight. Do not be alarmed that the cabin crew didn't react to the pilot announcements. They usually just consist of information they already know, like flight time and the weather, and are more focused on serving their passengers.

So if you were me, you cancel the ticket or just hop on the plane ? Thanks anyway for the explanation.

@droidnation if I were you I would acknowledge that I have a fear of flying, realise that so many other people have the same fear, and then seek professional help for it. There are many classes you can take to help overcome this fear. You don’t need to worry about the safety of commercial flying - it is more safe than walking down the street, so I hope you do get on the plane and have a great time.


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Which Airbus models have exterior LED lights? (Taxi, Landing, Rotating Beacon)
I know that the Boeing 737 MAX has LED'S. Which Airbus models also have LED external lighting?

If we are talking interior then most newer Airbus models have full led interiors. Like the newer 320 models and the A350. http://www.aircraft.airbus.com/newsevents/news-events-single/detail/airbus-lights-the-way-first-a321-with-led-lighting-throughout-the-cabin/

The A320NEO has full LED lighting. Check out the below link.
http://utcaerospacesystems.com/cap/systems/Interiors%20Documents/Lighting%20Systems/06%20Anti-Collision%20Lights/06_0010%20LED%20Anti-Collision%20Lighting%20System%20A320.pdf


text:
How reliable are aircraft cutaway drawings from Flightglobal?
I am working on a new system that would be retrofitted on jets (can't talk much about it yet), and I was looking for detailed drawings to start creating its detailed engineering design.
I stumbled upon this website, does any of you know how reliable Flightglobal and those drawings are / where they get their information? Your opinion would help a lot.
Thanks!

How critical is the system? Have you planned how to certify it with not knowing exact engineering detail?

These cutaways are just general representations of what structural components go into the aircraft; they are NOT engineering drawings nor should they be used as such.
In general the OEMs and the engineering departments for the airlines are pretty sensitive about releasing engineering data for proprietary reasons.  If you are working on a product closely with an OEM or an airline, they may be able to grant you a license to access such data, generally for a substantial fee. Or, if you have a client who will allow you access to the aircraft, you may be able to take engineering photos and/or make detailed measurements directly on the aircraft.

Thanks, that's what I expected but I still had a bit of hope... I'm also currently working on option 2 (access the aircraft and reverse-engineer the drawings) because, as you mentioned, OEMs are really sensitive about sharing this kind of information.


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What is the standard temperature used in this true altitude equation?
The control tower of a certain airport with true altitude of 2000ft informs the pilot that QNH is 900hPa and the temperature at the airport is -10 degrees Celsius. The airplane is at FL300 (vertically above the airport) and the OAT measured by the airplane sensor is -30 degrees Celsius. What's the true altitude of the airplane?
The teacher gave us the following formula
$$Z_v=Z_{QNH}+(Z_{QNH}-Z_t)\frac{4(T_v-T_{Std})}{1000}$$
but the question is. We have the $Z_t$ (2000ft) and $T_v$ (-30 degrees Celsius), we can calculate the $Z_{QNH}$, but what is the $T_{Std}$ ? Is it the temperature at the flight level considering the ISA Atmosphere or do we need to start with -10 degrees Celsius and calculate the temperature at FL300?

Look what ISA gives you for ground and air temperature and subtract the difference from the actual ground temperature.

@PeterKämpf, just to confirm, are you saying that $T_{std}=T(ISA){Ground}-T(ISA){air}-T(Real)_{Ground}$?

No, $T_{std} = T(real){Ground}-T(ISA){Ground}+T(ISA)_{air}$

Standard temperatures are based on the Standard atmosphere. A lapse rate, dry or wet depending on your environment, is used determine the standard temperature for a given altitude relative to the standard sea level temperature. The post, How does one calculate true altitude? may help you out here.


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What exactly is a 'hard landing'?
In my shareholder agreement, there is a very reasonable line that states:

Any hard landings to be reported immediately to [head instructor] or [club name]

The thing is, I'm not exactly sure where the line is, i.e. when does a non-great landing become a hard landing. The other day I flew into a challenging short-strip grass strip in moderate wind, bounced twice on the landing, added power, changed my mind, took power off, landed it just before the runway threshold, it was a mess. But the nose gear wasn't hit particularly hard.
How does one define a hard landing?

When you do it, you'll know :D

Possible duplicate: https://aviation.stackexchange.com/questions/1613/how-can-i-know-if-a-landing-exceeds-the-hard-landing-threshold-for-a-cessna-172s?rq=1 (Different aircraft, but answer likely to be the same)

If you're rubbing the seat of your pants after you get out of the plane then it probably was one.

It's the sort of landing where your passengers ask if you landed or crashed

If you are on a short strip and you bounce you should go around. Period. And if you have to ask if it was hard then you should report it.

In general aviation there isn't really a yes/no definition. It's a judgement call. As a newbie, and the owner of a shared aircraft, it's prudent to err on the side of caution and report anything more than minor bounces.
If it made you worry that you damaged it, it's hard enough to let someone know.  Especially if the nose gear came down hard, or worse, first, the nose gear being the more delicate element.
Golden rule: You get in way less trouble with other shareholder partners and the person maintaining the airplane by reporting non-damage than by not reporting damage. You may find that you'll report something, they'll ask you to describe it in detail, and they may just say don't worry about it.
Or, you tell someone you had a bad bounce, they'll go out and give it a once over by eyeball, and if the thing looks like nothing's changed, like one wing tip a little low to the ground, that'll be it. Or they may start pulling cowlings and access panels, but you've covered your behind.
In any case, you'll get brownie points as someone they can trust not to hide your embarrassments (because it's the people that hide that stuff that other pilots fear the most).
The benefit is you can then observe the result if the airplane gets checked over and a thumbs up/thumbs down given, and you added some new data to your internal knowledge and experience database that helps you next time decide what to report and what not to.
As far as the airplane is concerned, all that matters is, is something permanently bent, or worse, fractured/cracked/torn. If nothing's bent out of its original shape, it's fine. The weak points are the gear leg roots and the socket structure the gear leg plugs into for cantilever gear (of the equivalent points at the fuselage for a strut based main gear), and the nose gear's attachments to the firewall or engine mount.
The decision to ground yourself if you landed really hard at some outlying airport is a little harder. If that was the case, I would inspect the airplane myself and stand back and look at it to see if everything was normal and if nothing stood out I'd fly back, but I'd still report the event.
Everybody bounces their airplanes, and over time you'll learn what's worth bothering with, and what's not.

I would just add to the other answers to say that some aircraft have mechanical indicators showing that a hard landing has occurred.  For example, the Eclipse 500 VLJ has split rings on the main landing gear that are displaced in a hard landing to reveal a red painted ring, and a tab on the nose gear that gets bent in the event of a hard landing.  Either one indicates the need for an inspection prior to flying again.

The threshold for "hard landing" is usually defined by the aircraft manufacturer in terms of either the load factor or the descent rate at touchdown.
For example, according to this video by Mentour Pilot, the threshold for the Boeing 737 is 2.1g (peak recorded load factor) at touchdown, whereas it is 2.6g for A320 according to this source.
Mentour Pilot also explained in his video that:

...There is nothing in the cockpit that indicates how many G's we have exerted during the landing unfortunately. (...) The reason for that is that we are supposed to be conservative, so if we have any kind of doubt, it is better for us to report it as a hard landing and get the maintenance inspection done.

I question how useful an answer about a B737 is, when the OP is clearly talking about flying light aircraft ("short-strip grass").

@Jamiec The first paragraph of my answer says: "The threshold for "hard landing" is usually defined by the aircraft manufacturer in terms of either the load factor or the descent rate at touchdown." - this is the answer, and is applicable to all aircraft, irrespective of weather it's a bush plane or a passenger jet. I only used Boeing 737 as an example, because I could easily find reliable information regarding its "hard landing limit". If you're able to find any reliable information regarding any light aircraft, feel free to inform me.

@AdityaSharma that's an interesting point, but, respectfully, I think you need to justify your assertion that "hard landing" is defined by manufacturers. I would posit just the opposite, that manufacturers rarely publish this threshold. Perhaps in the case of defense and airline manufacturers this is not the case, but for typical light pistons and gliders I cannot recall seeing it in any POH or AFM I've read. Perhaps it's always been there and I've never noticed, but I remain skeptical until your assertion is supported.

@Jamiec Indeed, had OP done those two bounces and everything in a 737, there would have been no need to report it, it would have made the news.

As said in previous answers, there is not a real yes/no definition.
Let's use the Boeing 747 as an example:
When touching down on a Boeing 747, the pilot targets 60-180 FPM (Anything softer would be hard to aim). Mostly, according to my research, hard landings are usually landings above 250-300 FPM touchdown rate.

incorrect. That's a dangerously low vertical speed that's very likely to lead to floating and bouncing, missed touchdown points, or worse. You're supposed to land "firmly". What that is depends on the aircraft type, but for a 747 it'd probably be in the 300-500fpm range.

@jwenting: According to Raymer "anything above 4-5 fts would be considered a bad landing by most passengers". (240-300fpm).


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What is the aircraft type in the movie 'Once Upon a Time in Hollywood'?
Once Upon a Time... in Hollywood, a recent movie set in the late 1960s, has a few scenes in a Pan American Airways (Pan Am) aircraft. Looking at Pan Am's fleet at that time, it looks like it was either a Boeing 720B or a Boeing 707-320C. What type was it?
I have tried looking for images of the scene but couldn't find any. Hopefully, someone has watched the movie and can answer.

Yes, a screenshot would help, but he's obviously counting on answers from those who have seen the movie...

I don't know if it's possible but you should include a picture of the aircraft (screenshot of the movies?)

The first place I checked was the Internet Movie Plane Database but they don't have the movie listed yet.

I don't understand the downvotes as no comment seems to justify downvotes (a missing picture hardly justify a  downvote).

Internet Movie Plane Database now lists this film, with a screenshot showing a 747 with the tag  "Friday August 8th 1969" - indeed many months before the 747 was introduced. http://impdb.org/index.php?title=Once_Upon_a_Time_in_Hollywood

Presumably a wrong B747.
I haven't seen the movie yet but from all I read about it, it contains an airplane scene in which a wrong airplane is shown for the time the film is set. The Internet Movie Database (IMDB) lists two goofs (movie errors) related to aircraft in that movie:

Pan Am did not introduce the Boeing 747 until
  January, 1970, over five months after the
  Tate murders.
  (source)

and

When showing the 747 model in at least one of the
  flight scenes, the wrong model was shown. A model
  of a 747-800 series (with some of the windows edited
  out) was used. The 800 series didn't fly until
  the 2000's.
  (source)

Sometimes the trivia section also lists some information like The plane at 32:00 was a G5 but as of now there's no such hint for this movie and the B747 is just a guess because it is the only aircraft mentioned in the context of this film.


text:
Can I fly IFR in VMC if my instrument rating is not current?
If my IFR rating is not current, does this mean I can't fly by IFR, or does it just mean that I can't fly in IMC?
It seems that if it's just the latter, then it would make sense to fly IFR if the weather is still VMC. It would allow me to stay current on procedures while waiting for the opportunity to get my rating current.

You can file a VFR flight plan, at VFR altitudes and follow the IFR waypoints, but you must remain VFR. Do it "under the hood" with a safety pilot for the practice, ask for to fly the IFR approach even.  ATC will give it you, full approach & miss if you ask, or with vectors, but they'll tell you to remain VFR while doing it.  I just did the same with my instructor to get signed off for an Instrument Proficiency Check (IPC) in the Boston, MA area, even getting vectored around for other planes on IFR plans, in VMC conditions for the whole flight (nice sunny afternoon, no clouds).

No, you cannot. 14 CFR 61.57 (c):

(c) Instrument experience. Except as provided in paragraph (e) of this section, a person may act as pilot in command under IFR or weather conditions less than the minimums prescribed for VFR only if: [instrument currency requirements]

To accept an IFR clearance as PIC, even in VMC, you must be instrument current.

Just to throw a wrench in, when I was in training, before I had my instrument rating, the military would have us take IFR clearances, under some weird agreement that we were to remain clear of clouds (ie, the pilot would deviate if necessary), while we transited to and from the MOA and home field.  It wasn't VFR flight following, we had strict altitudes, heading assignments and even departure procedures we had to follow, but we weren't totally IFR either.  We operated in some sort of weird nebulous, FAR's be damned.


text:
What type of helicopter is shown in Star Wars The Last Jedi featurette?
There is a nice featurette about the new Star Wars movie The Last Jedi.
One shot (1:32) shows a helicopter in the background. What is it?

Nobody's asking the obvious question: What's a helicopter doing in Star Wars???  :D

The helicopter is a Eurocopter EC135 T2+. The registration (just above the tail rotor) EI-ILS shows that this aircraft was registered in Ireland, this helicopter was sold to PDG HELICOPTERS in early 2016 and is now on the U.K. register as G-GLAB. Based on this information it suggests that this particular segment was filmed before or shortly after early 2016 when the aircraft would likely have been re-painted with the new registration.
Eurocopter are a popular "household name" in aviation with numerous models operated throughout Europe and beyond in various roles such as airborne policing, medical flights (air ambulance), and some military operations. Eurocopter now operate as "Airbus Helicopters" and subsequently the EC135 has been re-designated as the H135.

Googling the registration EI-ILS:

Eurocopter EC135 T2
Irish Helicopters Ltd
MAX. PASSENGERS 6
YEAR OF PRODUCTION 2008
HOMEBASE EIDW (DUB), Dublin Intl

It also looks exactly like a EC-135, so google seems to be right.

You can read that?

@mike Its pretty clear if you zoom in on the image.


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Is there a 3rd-party API for aviation weather forecast, which includes additional cloud information?
I posted this question on StackOverflow here and terriblememory suggested I post it here.  I didn't even know there was an aviation stack exchange.  Cool!

I have been scowering the internet all day for a third-party weather
  API that reports more than just the cloud coverage for cloud
  information.  I need to know the height of the cloud.
I need something like an aviation weather API that reports either the
  cloud height, the cloud max and min vertical position, or the cloud type (Cirrus, Stratus, Cumulus, etc.) from which we could then derive the relative height.
We want the API to be free at least during development.

I found some relative information in this stack exchange and one answer here that tells how to find the cloud tops but I'm posting this question anyway in case there is an API yet to be suggested.
Meanwhile, I'll be taking a look at the other information I found in this stack exchange.  Thank you in advance for suggestions.

Normally, aviation weather reports (METARs) carry the cloud base height -- does this work for you?

Do you need observations or is model forecast data adequate?

I'm a programmer and we're looking for this information for Ballistic Missile accuracy.  It may be possible that cloud base height might help.

There has to be something out there else how would pilots know to climb to a destination altitude to get above the clouds? -> The kinds of aircraft that can easily get above the clouds are usually also those that are certified for flying in the clouds...so they don't really care.

METARs can be had quite easily from http://weather.noaa.gov/pub/data/observations/metar/stations/. However METARs only have cloud base, for the layers visible from the ground and only up to certain altitude. So if there is an overcast layer, there is no information about any layers above it and if there are no clouds below 5,000 ft or 10,000 ft simply report "CAVOK" or "NSC" (no significant clouds). You may get CAVOK and it might still be overcast at 6,000 ft.

Who're you working for that has ballistic missiles but no access to a weather forecast?

We have access to weather forecast.  That's not the issue.  If there is a weather forecast application out there that determines "cloud height", it must be Top Secret.  We don't have ballistic missiles; we provide software to others who may or may not have them but support someone who does.  Anyway, lesson learned, cloud height appears to be difficult to get from any weather app out there to date.  Maybe in the future.

There isn't a simple easy-to-use API for this, but there is a plethora of model data you can use to derive a proxy for cloud locations.  Specifically the GFS and ECMWF both run global forecast models and there are various regional models (e.g. in the US we have NAM, RAP, HRRR, ensembles and various high-res WRF runs).  The GFS, for example, provides relative humidity and cloud water mixing ratio at its vertical gridpoints and from these you could model where clouds are likely to be.
It is certainly possible to model cloud bases with publicly available datasets as demonstrated by the folks at SunsetWX can attest to, as cloud base heights play a role in vivid colors at sunset.
This won't be an easy-to-query API, but well within the research of someone willing to work with existing forecast and observational data (satellite (visible, IR, water vapor), soundings, profilers, radar, etc) to build a predictive cloud location model.  There may already be published literature on this and you might get more information over on Earth Science stack echange if that is the case or if there is some dataset already out there that I'm not personally aware of.

Thank you, casey, for your suggestion.  There is a lot of information on this subject on the Earth Science stack exchange.  Unfortunately, as @JohathanWalters says in his answer, there is no such API.  I wish I could give the points to both of you.

Short answer:
I wish this information were available, but what you are looking for is simply not available.
Longer answer:

There has to be something out there else how would pilots know to
  climb to a destination altitude to get above the clouds?

You are looking for data that you rightly think should exist. I would that it did, but it doesn't. Thats where the art of airmanship comes in. The answer to your question I quoted above is a complex mix of years of experience reading the weather charts, eyeballing the view out the window, and networking through the radio.
Real world weather is too hard to predict, and is constantly in flux. The only way to know the actual cloud conditions is to get out there and see it in the moment. The ground based weather observation stations like AWOS and ASOS do a decent job, but they are very limited and often wildly inaccurate. They only provide an assessment what is visible straight up.
PIREPS are the only partial answer you will get, and these are sparse and dated. A PIREP is only a snapshot of what a pilot observed at one place at one time.
Area forecasts will sometimes include a cloud top forecast (look for "TOP FL200" or similiar). However, a forecast—especially an area forecast which often covers half a state—is vastly different than an observation.
You've already mentioned Skew-T charts, and they do have useful data. Depending on your application, this might end up being your best bet. If you want something that doesn't have a real world aviation application (e.g. for the SIM community), you could derive your sought information from this.

You are correct.  There is no such API.  However, I did find more information in the Earth Science stack exchange after receiving the suggestion by casey in his answer.  I'm leaving this question here in this exchange just in case it helps somebody else.  I wish I could give the points to both of you.

@MissLucy Oh, I don't care about points! Glad you found useful information :)


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Why has CFM International changed the profile of the fan struts used at their CFM 56 turbofan?
The shape of the horizontal struts has changed. See images with arrows indicating the struts cited:

Image of a early version of a CFM56 turbofan showing the fan struts

Image of a CFM56 7B26 showing the fan struts

Maybe it hasn't changed, only that the aft airfoil-ish part of the strut was omitted from the first display model (which also lacks a bunch of plumbing and wiring).